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					The Forward Vertex Upgrade
    Detector for PHENIX

           Sergey Butsyk
   for the PHENIX Collaboration
                 Outline
•   Muon Identification in PHENIX
•   FVTX detector for Muon Arm Upgrade
•   Displaced vertex muon tagging
•   Signal to Background improvement
•   Future Outlooks
                PHENIX Detector
• Muon
  measurements
   – 1.2 < |h| < 2.4
   – Two separate arms
     in forward and
     backward rapidity                                m+


• No vertex tracking                                  m-
   – All particles assumed
     to come from primary
     vertex measured by
     Beam-Beam Counter


                             Space for Vertex upgrade detectors
          Muon Sources in PHENIX
           Muon ID     Muon Tracker   Absorber



                                                        Collision




                                                        Muons
                                                        Hadrons


• Muon arm consists of several layers of detectors and
  hadron absorbers
• Muon candidates consists of        for current analysis
   –   Prompt muons                              Background
   –   Heavy flavor decay muons                    Signal
   –   Hadronic (p,K) decay muons                Background
   –   “Punch through” hadrons                   Background
              Single Muon Analysis
•   Analysis in p+p and Au+Au suffers
    from large hadronic background

•   Strongly relies on hadron
    production yields and interaction
    cross sections for absorber
    material

•   Need to improve background
    rejection capabilities

•   No accurate vertex information, all
    particles assumes to come from
    primary vertex

 Propose to upgrade PHENIX
  muon arm with precision tracking
  detector
FVTX Muon Arm Upgrade




      • 4 discs of Si sensor in acceptance of
        each Muon Arm
      • 75 mm pitch strips accurately measure
        R coordinate of track
      • Scheduled to be installed in FY11
          FVTX Detector Elements
                                                           Backplane
                                                          HDI
                             11.2mm            Detector

                                      FPHX Chips




•   4 disks / side
•   48 wedges/disk
•   75 um strips,
•   2.8-11.2 mm long
•   1664 strips/column
•   1.1M channels total
•   Readout with FPHX chip   2.8mm     Rigid, thermally                Rigid epoxy
                                      conductive epoxy
            Design Strategies
                                          prompt




                                        pm




• Fitted track provides a DCA to the primary vertex
  (measured by central arm barrel VTX detector)
          DCA Performance



                                             300 mm
                   100 mm




• Tracking uses Kalman fit to all the hits from
  FVTX and Muon Arm (also include VTX hits)
    DCA for Signal and Background
•   DCA depends both on decay length
    and decay angle
•   Hadron decays are easy to suppress
    due to large decay distance
•   DCA in f already rejects a significant
    portion of hadronic background                   fvtx




                         hadrons


                                             K   D          B

                         D decay




               B decay



                                   cm
              Radial DCA and c2 cuts
• Adding FVTX hits into Muon
  arm help to remove hadronic
  decays between FVTX and
  MuTr
• c2/n for those tracks is a clear                            hadrons
  cut parameter

                                                    D decay

   D decay
                                          B decay
                hadrons

                                                                        chi2

                           • Radial direction is much more precise for
                             DCA measurement
    B decay                • B and D meson decay muons produce
                             asymmetric DCA distributions due to large
    Cut
   region
                             decay angle
                           • Cut on negative DCAr improves S/B
                      cm     substantially
    Heavy Quark S/B improvement




                                                   x 10 improvement
•   Signal to background improves by a factor of
    10 over the whole range of measurements
•   At the same time recover 20-30% after all
    the cuts
•   Both statistical and systematic errors on
    Heavy Flavor signal improve due to the
    smaller background uncertainties
    contribution
Heavy Flavor Signal Expectations




• Error bars show combined systematical and statistical error on
  Open Charm single muons
   – Red : Year2 p+p results
   – Blue : Same data with FVTX detector background rejection
             Physics Outlook with FVTX




•   Wide variety of physics probes
    can be measured with increased
    precision with FVTX detector
     – Double spin asymmetry ALL
     – Open Charm nuclear modification
       factor RAA
     – J/y and y’ in p+p and Au+Au
     – Muons from W decay
         Construction Schedule
                     2008     2009      2010         2011    2012

  VTX
                               pixels   stripixels
  FVTX

         R&D Phase          Construction Phase          Ready for Data


• Barrel VTX construction well underway
  – pixel layers completion in 2009
  – stripixels completion in 2010
• FVTX detector construction started in
  FY08, installation to be in 2011
                 Conclusions
• FVTX detector upgrade significantly improves
  hadronic background rejection for all muon arm
  physics observables

• Tagging displaced vertexes of Heavy Flavor semi-
  leptonic decays with FVTX detector is a feasible task

• S/B for the Open Charm and Open Bottom single
  muons improves by a factor of 10 while leaving a large
  portion 20-30% of the signal after the cuts

• Detector is approved by DOE for construction (starting
  April 08) and planed to be put into operation in FY11

				
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